Casting more uncertainty over the presidential nominating process for 2008, the Florida Legislature on Thursday moved the state’s primary up to Jan. 29, ignoring the threat of sanctions from the national Republican and Democratic parties.

The new date puts the Florida primary ahead of all but four states. State party leaders hope that it will give Florida, the most populous swing state, a bigger role in choosing presidential nominees.

But officials in other states said Florida’s move would only create more chaos around the nominating process, which has already been upended by other states’ decisions to hold earlier primaries. New Hampshire may move up its primary as a result — possibly even to this year, political leaders in other states said. And in South Carolina, Republican officials said they, too, would advance the date of their own primary.

“South Carolina will name a date that keeps us first in the South,” said the chairman, Katon Dawson. “It could be as early as Halloween and our version of trick-or-treat, if we have to.”

Choosing primary dates has always been contentious, with states that held primaries late in the season feeling marginalized. But frustration soared this year, and dozens of states began to jostle for position, with more than 20 so far settling on Feb. 5, or considering it.

The shifting dates have forced the presidential campaigns to reconsider every aspect of their nominating strategy — where to compete, how to spend money, when to start television advertising.

Both parties have been trying to put a halt to the leapfrogging. They have said they would penalize all but a handful of states if they hold a primary before Feb. 5, stripping them of half their delegates to the national nominating conventions. Under Democratic Party rules, the candidates can also be penalized, losing the delegates they won in the rule-breaking state.

But Florida officials scoffed at those threats, calling the conventions little more than a formality.

“We have people who get invited to a big party where they drop a balloon and people wear funny hats,” said Marco Rubio, the Republican speaker of the state House of Representatives. “But they don’t have any role to play.”

He added, “At the end of the day, the truth of the matter is that the nominee of either party is going to want to make sure they have not offended the big donors and the biggest activists in the most important state in the country that is electorally available.”

Some of the states that have moved up their primaries to Feb. 5, including California, Connecticut, New Jersey and New York, said they did not expect to seek even earlier dates.

“I just don’t see it as likely,” said Ron Nehring, chairman of the California Republican Party. “California is going to be relevant, regardless of what other states choose to do.”

In addition to New Hampshire, the states with contests before Jan. 29 are Iowa and Nevada.